I recently saw a 4650 512mb for about £34 at pixmania on hot deals when I came accross this.
This is a 1GB and unlike the one at pixmania this has a 128-bit memory bus and not the crippled 64-bit
The graphics card in general is perfect for those who have a low budget and it can handle games quite well.
This was the cheapest what I could find anywhere. You can collect at store or have it delivered for an additional £2.34.
Follow link to view more info.